In general, a bulletproof helmet refers to a helmet that deflects a shell flying from the outside.
In our country, a steel helmet has been used as a military bulletproof helmet since the Korean War. Like another bulletproof helmet, the steel helmet is a helmet which is made of steel and is produced so as not to allow a shell of a small arm, fragments of a bomb or a cannonball or fragments of a rock to penetrate the helmet. The shape and material of the steel helmet are different in countries, but most steel helmets have a weight of about 1 kg. In order to increase the strength of the helmet cover, the steel helmet has been made of a steel material such as a special alloy including nickel, manganese, chromium, and silicon.
In recent years, the steel helmet has been replaced with a nylon helmet due to the weight and performance. The nylon helmet has been developed in 1974, and has been gradually supplied to the Korean military. Such a nylon helmet was used in the early 2000's. The nylon helmet has been used in partial rearguard units up to now in 2010, and as the bulletproof ability of the nylon helmet is doubted, a new model helmet has been strategized in the second half of 2003, as a self-develop business.
In order to increase the survivability of the Korean military, the new model helmet of the Korean military improves the bulletproof performance by 2.2 times (900→2,000 ft/sec) greater than that of the existing helmet. The helmet which is used in the advanced countries and has a bulletproof performance of 2,000 ft/sec has a weight of 1,300 g or more, whereas the new model helmet has been known as the lightest helmet having a weight of 1,150 g.
A depending ability of the M1 steel helmet called the Korean military bulletproof helmet merely defends fragments, and does not defend the shell. The M1 steel helmet does not defend even one 9-mm parabellum shell. Meanwhile, a Fritz helmet (US army) defends four shells without any defect.
The purpose of the bulletproof is to bounce the shell of the enemy in the actual situation (a distance of about 200 M). However, when the shell is directly shot at the currently used bulletproof helmet, the shell penetrates the helmet within an effective shooting distance even through the pistol or the rifle is used.
In the most recent year, a bulletproof helmet produced by a method in which a light, strong aramid-fiber fabric is mixed with an adhesive and the mixture is press-molded with high heat has been introduced, and since the produced helmet is lighter and stronger than the steel, this helmet has been widely used. However, since this helmet has a semicircular shape, there is a problem that the helmet is highly penetrated by the shell as it goes toward the upper end from the curved upper end of the bulletproof helmet.
Even though this helmet defends the shell, there are dangers of brain damages and serious neck injuries due to the shock.
Thus, it is necessary to achieve the safe of a wearer by increasing the thickness of the bulletproof helmet to increase the bulletproof performance. However, in this case, since the weight of the bulletproof helmet is increased, the herniated cervical disc of the wearer may be caused, and the combat capability thereof may be degraded.
In order to solve the problems, a bulletproof helmet made of an aramid fiber having light weight and excellent bulletproof performance is recently introduced. Such an aramid fiber is not sufficient as a composite material for bulletproof requiring excellent light properties due to its high specific gravity of about 1.44. A composite material for bulletproof manufactured using an aramid fabric impregnated with a typical resin such as a phenol resin has a problem that the bulletproof performance is degraded since the adhesive strength is degraded between the aramid fabrics.
For reference, as the documents regarding the related arts regarding the bulletproof helmet, for example, there are Korean Patent Publication No. 10-2011-0070118 (Application date: Dec. 18, 2009; ANTI-BALLISTIC PROTECTIVE COMPOSITE AND ANTI-BALLISTIC PROTECTIVE HELMET MANUFACTURED BY USING THE SAME) and Korean Utility Model Registration No. 0392560 (Application data: May 13, 2005; PROTECTIVE HELMET).
There are not currently bulletproof helmets having the defending ability capable of perfectly depending the direct shooting of the rifle shell including the technologies of the above-described documents.
Accordingly, there is a need for development of a bulletproof helmet capable of preventing the bulletproof helmet from being penetrated to relieve the shock by accurately deflecting the entering shell while minimizing the weight by producing the thickness of the helmet.